The invention herein presented relates to Unmanned Aerial Vehicles (UAVs), that is the same as Remote Pilot Vehicles (RPVs), or "drones", which carry a payload (i.e. TV camera) and used, for example, for surveillance and reconnaissance. More particularly, the invention pertains to the Traffic Collision Avoidance Systems and to interoperability between UAVs and other piloted or unmanned aerial vehicles and tall on-ground obstacles.